Connection Strings in Oracle
Example: User Id=scott;Password=tiger;Data Source=bbSales12
In this case
bbSales12 is an alias.
To resolve this alias, Oracle first looks in "the connection pool" to see if it has already "Resolved" that alias.
Next it looks in
tnsnames.ora is a file that contains enough configuration detail that your machine should be able to connect to the remote machine.
How does Oracle find the tnsnames.ora file?
Oracle relies on an environment variable, TNS_ADMIN
If you don't have this environment variable set, then Oracle will not be able to find the tnsnames.ora file (or the sqlnet.ora file, which will be described later)
tnsnames.ora you should find the alias defined via a piece of configuration language like this:
bbSales12= (DESCRIPTION= (ADDRESS= (PROTOCOL=tcp)(HOST=bb12Sales-server3)(PORT=1521)) (CONNECT_DATA= (SERVICE_NAME=sales.us.acme.com)))
You can also use "Easy Connect Naming Method"
Instead of an alias, you specify a datasource in this form:
"user id=scott;password=tiger;data source=//bb12Sales-server3:1521/sales.us.acme.com"
But note that:
Prior to using the easy connect naming method, make sure that EZCONNECT is specified by the NAMES.DIRECTORY_PATH parameter in the sqlnet.ora file.
"sqlnet.ora" is a file which is also searched for in the TNS_ADMIN folder
Inside that file, if you specify
NAMES.DIRECTORY_PATH= (TNSNAMES, EZCONNECT)
...then you'll be able to use "the Easy Connect Naming Method".